fix(bluebubbles): add GUID-based dedup to prevent duplicate replies

[rswafford1980]

Problem

BlueBubbles sends multiple webhook events per incoming message (5-10 POSTs in rapid succession as iMessage status updates fire: delivered, read, etc.). The _handle_webhook method in bluebubbles.py spawns asyncio.create_task(self.handle_message(event)) for every webhook hit.

Although handle_message() in base.py has an _active_sessions guard, the tasks are spawned synchronously but run asynchronously, creating a race window where multiple tasks pass the guard before the first one sets it. Net result: every iMessage gets 2+ duplicate replies from the agent.

Fix

Three changes in gateway/platforms/bluebubbles.py:

1. Add import time to imports
2. Add _seen_message_guids dict and _DEDUP_TTL = 30.0 to __init__
3. Add GUID-based dedup check in _handle_webhook — before the handle_message spawn, checks if the message GUID was seen within the last 30 seconds. If so, returns ok immediately. Periodically prunes expired entries.

The dedup runs after the existing isFromMe and tapback filters, so those are unaffected.

Test Plan

• Verify single reply per iMessage on macOS with BlueBubbles private API enabled
• Verify dedup cache prunes stale entries (no unbounded growth)
• Verify isFromMe and tapback messages still silently dropped

[alt-glitch]

Duplicate of #18395 which implements BlueBubbles webhook dedup by message GUID+chat. Also overlaps with the dedup component of #11654.

[teknium1]

Thanks for isolating the inbound webhook duplication path.

Problems

• gateway/platforms/bluebubbles.py:70 deliberately admits updated-message events. The GUID-only check added by this PR would drop every same-GUID update, not only identical webhook replays; it needs an event/update fingerprint that preserves meaningful lifecycle updates.
• The new local cache duplicates gateway/platforms/helpers.py:27-71, where MessageDeduplicator already provides TTL pruning and a hard size bound.
• The diff has no tests, despite an existing webhook suite in tests/gateway/test_bluebubbles.py. Regression coverage should exercise exact replay suppression and same-GUID lifecycle updates.

Suggested changes

• Reuse MessageDeduplicator and key it with a replay fingerprint rather than GUID alone.
• Add focused async webhook tests for replay, distinct GUIDs, and same-GUID update/attachment behavior.

This is an automated hermes-sweeper review.

[teknium1]

Please reuse gateway.platforms.helpers.MessageDeduplicator rather than adding a second local TTL map. The shared helper already enforces a maximum cache size in addition to TTL pruning.

[teknium1]

This suppresses every same-GUID event, but the adapter explicitly accepts updated-message events. Use a replay fingerprint that distinguishes exact retries from meaningful same-GUID lifecycle updates such as edits or attachment completion.